Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

[Sally Furniss]

Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

<!-- end title area --> <!-- start authors --> http://pathogens.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.ppat.0030151


Anice C. Lowen¹^*, Samira Mubareka¹, John Steel¹, Peter Palese^1,²^*
<!-- end authors --><!-- start affiliations --> 1 Department of Microbiology, Mount Sinai School of Medicine, New York, New York, United States of America, 2 Department of Medicine, Mount Sinai School of Medicine, New York, New York, United States of America

<!-- end affiliations --><!-- start: abstract --> Using the guinea pig as a model host, we show that aerosol spread of influenza virus is dependent upon both ambient relative humidity and temperature. Twenty experiments performed at relative humidities from 20% to 80% and 5 °C, 20 °C, or 30 °C indicated that both cold and dry conditions favor transmission. The relationship between transmission via aerosols and relative humidity at 20 °C is similar to that previously reported for the stability of influenza viruses (except at high relative humidity, 80%), implying that the effects of humidity act largely at the level of the virus particle. For infected guinea pigs housed at 5 °C, the duration of peak shedding was approximately 40 h longer than that of animals housed at 20 °C; this increased shedding likely accounts for the enhanced transmission seen at 5 °C. To investigate the mechanism permitting prolonged viral growth, expression levels in the upper respiratory tract of several innate immune mediators were determined. Innate responses proved to be comparable between animals housed at 5 °C and 20 °C, suggesting that cold temperature (5 °C) does not impair the innate immune response in this system. Although the seasonal epidemiology of influenza is well characterized, the underlying reasons for predominant wintertime spread are not clear. We provide direct, experimental evidence to support the role of weather conditions in the dynamics of influenza and thereby address a long-standing question fundamental to the understanding of influenza epidemiology and evolution.

<!-- end abstract --> <!-- start footnote section -->Funding. This work was supported by grants from the W. M. Keck Foundation, the Centers for Disease Control R21 (U01CI000354–01), and the Center for Investigating Viral Immunity and Antagonism (1 UC19 AI062623–023) (to PP). ACL is a Parker B. Francis Fellow in Pulmonary Research. SM was supported by Sunnybrook Health Sciences Centre, Toronto, Canada, and a Ruth L. Kirschstein Physician Scientist Research Training in Pathogenesis of Viral Diseases Award (Mary Klotman, P.I.). PP is a senior fellow of the Ellison Medical Foundation.

Competing interests. The authors have declared that no competing interests exist.

Editor: Ralph S. Baric, University of North Carolina, United States of America

Citation: Lowen AC, Mubareka S, Steel J, Palese P (2007) Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature. PLoS Pathog 3(10): e151 doi:10.1371/journal.ppat.0030151

Received: July 11, 2007; Accepted: September 5, 2007; Published: October 19, 2007

Copyright: © 2007 Lowen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abbreviations: Ct, cycle threshold; p.i., post-inoculation; PFU, plaque-forming units; RH, relative humidity
* To whom correspondence should be addressed. E-mail: anice.lowen@mssm.edu (ACL), peter.palese@mssm.edu (PP)

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

my summary:


transmission of influenza A/Panama/2007/99(H3N2) between
Guinea pigs depending on temperature and relative humidity:

temperature in degree Celsius
   |           |           |
  |05          20          30
--|-----------------------------------
20|.           .xxxxxxx
35|.xxxxxxxx   .xxxxxxxx   .
50|.xxxxxxx    .xx
65|.xxxx       .xxxxxx
80|.xxxx       .
--|-----------------------------------
|
|_relative humidity in %

x: one infected guinea pig (out of 8)

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

now, just let's look at the weather data.
What's the correlation between temperature,
humidity and flu-cases ?

Let's also see, how this varies between different flu-strains
to determine how much virus stability contributes
vs. host factors. (pages 1473,1474)

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

just quickly checking outdoor yearly temperature,

about 4,2 (6,0) guinea pigs out of 8 should get infected

in winter,summer in SanFrancisco (New York)

SF: 15,20 degrees, 70%(+-10) humidity
NY: 0,25 degrees, 55%(+-15) humidity

 

[Sally Furniss]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

Transmission of H5N1 between birds is fecal-oral route.

Transmission of influenza to the guinea pigs was by aerosol.

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

here an early paper about transmission of H5N1 in chickens
http://birdflubook.com/resources/shortridge331.pdf
(they conclude fecal-oral is dominant)

but then they found, that chickens, ducks have higher concentrations
of H5N1 in the pharyngeal fluid than in the feces.

respiratory transmission had been shown in tigers,cats,humans.
Probably also birds, I'm not sure ATM

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

Karo-Cluster, North-Sumatra, May 2006

H2H assumed.

temperature: 24(night)-32(day)
RH: 75-85


...it shouldn't have happened.
Or assume more favourable conditions at that time ... would we have got
an epidemic or pandemic ?


Also, Indonesia,Egypt,Hongkong,Vietnam,Thailand - the hardest
hit regions have unfavourable flu-aerosole-guinea-pig-conditions



should we keep RH at 50 or 80 in rooms during flu-waves ?
has it been tested ? (some hospital, nursing home, old
people's home, school)

or do people get it when they are outside in winter ?
Is it known, has it been examined ? If not, why ?

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

the virus has a coat, which is taken from the host-cell-membrane.
Can this coat influence it's stability or transmission as function
of temperature and humidity ?


why do they claim for temperature and humidity dependance
of seasonal flu, but didn't examine the correlation of flu
outbreaks, RH+temp. in historical human data ?

That's much more expressive than some guinea pig trials, IMO.

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

http://jvi.asm.org/cgi/content/full/81/11/5429


Indoor heating. Paralleling the direct effects of temperature and harsh weather on the biology of either the host or the pathogen, human defenses against declining temperature may themselves contribute to the seasonality of influenza. Indoor heating levels should increase as the temperature drops, resulting in a continuously recirculated body of air with very low humidity. These conditions are ideal for the persistence of viral particles in the environment, with the typical furnace filter incapable of effectively filtering the very small particles to remove them from the circulating air, although this may be offset by inactivation of the virus at high temperatures. Lack of a concurrent increase in influenza virus infection in summer, when the use of air conditioning systems is high, may largely be the result of the mechanistic differences between the two systems. Air conditioning lowers the absolute humidity of the air via condensation (potentially trapping virus-bearing aerosols within the unit itself), while heating lowers only the relative humidity and never exposes the air to a wet condensing surface. Large-scale heating systems, such as those in apartment buildings, offices, and university dormitories would create a viral dispersion mechanism resembling the unintentional one potentially responsible for the Amoy Gardens severe acute respiratory syndrome outbreak (50). Thus far, this theory, though consistent with other hypotheses governing seasonality, has not been discussed in the literature or examined empirically in the case of influenza, although levels of indoor air pollution, which would be continually recirculated in the winter, have been shown to be risk factors for lower respiratory tract infections (70). Mathematical models have also been developed which examine the risk of indoor, airborne infection risks. Small changes in ventilation accounted for dramatic changes in the reproductive ratio (R0; the number of secondary infections each primary infection gives rise to in an entirely susceptible population) for influenza virus, although the authors examined the risk of infection for single outbreaks and did not discuss mass ventilation changes such as those that may accompany the onset of winter as a potential driver of influenza seasonality (51).



On a population level, an entire city experiencing an epidemic could produce staggering amounts of virus aerosols, yielding something not unlike the medieval concept of infective miasma. It has been suggested that this mass of infective particles is responsible for the seasonality of influenza by using global convective currents in much the same way as the ventilation system of the Amoy Gardens housing complex used air currents. Originating in Asia during the winter, aerosol particles may be conveyed into the upper atmosphere by frequently forming cyclogenic systems. Here, the low temperature and relative humidity of the upper atmosphere may enhance long-term survival of viral particles, allowing them to be picked up by a westerly air current and transported to North America within the span of a few weeks. Once over the North American continent, they are forced lower by frequent cold fronts. In the summer, the atmosphere over North America is less favorable to dispersion, and South Asian pressure systems are weaker and shift directions, severely depleting the flow of particles and, therefore, yielding the observed seasonal patterns of infection (39).

 

[Shannon Bennett]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

I would like to add another missed fact. UV light destroys the virus. Airborne virus would be more likely to be eliminated in areas with strong sunlight. Areas with high particulates would not fare as well, as virus can remain hidden in the pollution particles. Shorter daylight hours in winter would also contribute to higher numbers of viable airborne virus.

The highest probability of airborne infection due to climatic conditions would be from the following criteria.
1. Dry cold air.
2. Indoor heating resulting in very dry indoor air.
3. Shorter daylight hours.
4. Very poor air quality with high numbers of particulates (smog).

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

... and then we have SE-Asia, the source of
most new flu-strains and two flu-seasons per year
and Indonesia the hotspot of H5N1 with

1. wet warm air
2. little indoor heating
3. long days
4. I don't know

 

[gsgs]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

did they stop these promising,interesting guinea pig experiments
or have they gone secret ?

--------edit1-------------
pubmed Palese:

http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
Oseltamivir-resistant influenza A viruses (H3N2,E119V) are transmitted efficiently among
guinea pigs by direct contact but not by aerosol.
----------------------------------------------------------------
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=18367530
High Temperature (30°C) Blocks Aerosol but Not Contact Transmission of Influenza Virus
Our data imply that contact or short-range spread predominates in the tropics and offer an explanation for the lack of a well-defined, recurrent influenza season affecting tropical and subtropical regions of the world.
-----------------------------------------------------------------
http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
Influenza virus transmission: basic science and implications for the use of antiviral drugs during a pandemic
----------------------------------------------------------------


Mubareka:
:
Variation in mortality rates among long-term care facilities for residents with lower respiratory tract infection.
Nicolle LE, Mubareka S, Simor A, Liu B, McNeil S, Lewis D, Duckworth H, Cheang M, Loeb M.
Infect Control Hosp Epidemiol. 2008 Aug;29(8):754-9.
PMID: 18624650 [PubMed - indexed for MEDLINE]
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[Shannon Bennett]

Re: Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

GSGS, perhaps that is why we don't have a pandemic already. Optimal temperatures and humidity do not preclude virus spread, it only aids in the spread. This might explain why we only rarely have flu pandemics. Where infected waterfowl and people mix intimately, is where warm moist air is predominant. If we saw pandemic strains of flu in downtown Beijing during winter months, perhaps H5N1 would already be an historical event.

It would be instructive to quantitatively measure flu spread in Beijing as opposed to Lima, Peru or, perhaps Edinburgh, Scotland.